What demographic trends produce a Type II survivorship curve in a population of rodents?

A Type II survivorship curve is characterized by a relatively constant mortality rate throughout the lifespan of individuals in a population. This means that rodents, in this case, experience a roughly equal chance of dying at any age.

To produce a Type II survivorship curve in the demographic data for a rodent population, we would expect several key trends:

  • Consistent mortality risk: The likelihood of death should be uniform across all age groups, suggesting that external factors, such as predation or disease, impact all age classes similarly.
  • Stable population environments: A stable environment with few drastic changes in resources or threats may contribute to a balanced mortality rate. For instance, a habitat where food availability and shelter are consistent could lead to equal survival probabilities.
  • Predictable reproductive patterns: If the rodents reproduce at a steady rate, with offspring having similar survival rates regardless of their age, this stability could support a Type II curve.
  • Social structure: If the rodent population has social behaviors that promote group living, it can help reduce the risks of mortality for all age classes, leading to this survivorship pattern.

In summary, for a rodent population to exhibit a Type II survivorship curve, we would expect demographic data to reveal consistent mortality rates across all ages, a stable environment, predictable reproductive behavior, and social structures that support equal chance of survival.

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